The present invention relates to a moisture curable composition which is curable even at ordinary temperature, and more particularly to a moisture curable composition containing as a main component a polymer having a moisture reactive organic silicon group (hereinafter referred to as "silicon functional group") in at least one polymer chain end and capable of providing an elastomeric cured product.
It has been attempted to use a methacrylate or acrylate polymer having a silicon functional group as a sealing material and a pressure sensitive adhesive. As a general process for introducing the silicon functional group into a methacrylate or acrylate polymer, there is mentioned a process in which an acrylate or methacrylate is copolymerized with an unsaturated compound having a silicon functional group such as vinyltrimethoxysilane or .gamma.-methacryloyloxypropyltriethoxysilane. However, the copolymer obtained by this process has the silicon functional groups randomly introduced in the polymer chain. Therefore, in case that the copolymer is a low molecular polymer, the cured product, namely the crosslinked product, has the defect that the elongation is low because the space between the crosslinking points is small. For giving the cured product having a high elongation, it is necessary to make the molecular weight of the produced copolymer large and to decrease the amount of the silicon functional group-containing monomer to be copolymerized so as to increase the space between the crosslinking points. However, the copolymer having a high molecular weight is a high viscous or solid substance, and accordingly when it is used as a moisture curable amorphous sealing material or pressure sensitive adhesive, it must be dissolved in a relatively large amount of an organic solvent and used in the form of a solvent solution. The sealing material of solvent type has the disadvantage that the shrinkage due to evaporation of the solvent occurs or the adhesion property is lowered by the use of the solvent. Also, the pressure sensitive adhesive of solvent type has the disadvantages that a long time is required in drying the adhesive coated onto a substrate such as a film to evaporate the solvent and the use of the solvent may cause a fire or exert a bad influence on the human body.
For eliminating the above problems and obtaining a sealing material or pressure sensitive adhesive having excellent properties, it is desirable to use a copolymer which has a relatively low molecular weight, in other words, which is a substance having a sufficiently low viscosity, and which has functional groups capable of causing crosslinking or chain extension reaction in the copolymer molecular ends as abundantly as possible, namely the so-called telechelic low polymer. Since the molecular weight of the telechelic low polymer is low, the viscosity of the polymer itself is low and the polymer can be used without a solvent or in the form of a solution of high solid content. Also, since the functional groups are present at the polymer chain ends, the space between the crosslinking points is large, thus there can be obtained a cured product having a high elongation and consequently sealing materials and pressure sensitive adhesives having excellent properties.
It is an object of the present invention to provide a telechelic polymer capable of being easily cured and suitable for use in a sealing material and a pressure sensitive adhesive.
A further object of the invention is to provide a moisture curable composition containing an acrylate or methacrylate polymer having a moisture reactive silicon functional groups and capable of providing an elastomeric cured product.
These and other objects of the present invention will become apparent from the description hereinafter.